Adenylate Cyclase Is the Enzyme Which Converts ATP to 5'-CAMP

Adenylate cyclase is the enzyme which converts ATP to 5'-cAMP. What is the expected effect on the in vivo expression of the lactose operon of a nonsense mutation in the adenylate cyclase structural gene (which totally inactivates the enzyme) ?

A) No effect under any environmental conditions.
B) the operon is transcribed at a high rate when cells are grown in a mixture of glucose plus lactose.
C) The operon is transcribed at a high rate when cells are grown in a mixture of glucose plus lactose.
D) The operon is transcribed at a high rate in the presence of lactose but a low rate in the presence of glucose and lactose.
E) The operon is not efficiently transcribed in the presence of lactose.